+
decreases the HNOa/(Th U) mole ratio necessary to solubilize the thorium and uranium. Containment of concentrated nitric acid a t temperatures above 250’ C. will probably require special materials of construction such as tantalum or titanium. The rates of corrosion of Type 347 stainless steel determined in nitric acid systems where the oxygen overpressure was a t least 150 p.s.i. increased with both increasing nitric acid concentration and temperature. With 1 and 2 M ” 0 3 , however, the rates were not excessive, being generally less than about 80 mils per year (Table 111). I n one test with 4M ” 0 3 , the rate was about 220 mils per year; severe corrosion was encountered in a test with 10M “ 0 3 . Savich and Howard (7) reported excessive corrosion of Type 347 stainless was used to oxidize steel pressure vessels when 4.5M “ 0 3 coal in the presence of oxygen.
tures and pressures may not be a severe limitation of the PAC process. The PAC process, using dilute nitric acid, could be used first to burn the graphite matrix and particle coatings. T h e uranium and thorium oxides remaining after combustion could then be dissolved in another reagent-boiling 13M HN03-0.05M HF, for example-at atmospheric pressure to produce a solution containing uranium and thorium in concentrations of at least 0.5M. Ac knowledgment
The authors are indebted to F. L. Culler, Jr., for suggesting the use of pressurized aqueous methods in the processing of nuclear reactor fuels. They also thank J. B. Farrell, D. A. McWhirter, J. F. Land, and C. T. Thompson for aid in conducting the experiments. Analyses were provided by the ORNL Analytical Chemistry Division.
Conclusions
literature Cited
The pressurized aqueous combustion process for graphitebase nuclear reactor fuels containing carbon-coated carbide fuel particles appears technically feasible. When excess oxygen was present, the net combustion reaction was C 0 2 C o n ,without consumption of nitric acid. Reaction rates were about 0.2 gram of graphite oxidized to C O S per hour per gram of graphite. Although most of the tests were made with 1 and 2M HIio3 a t 275’ and 300’ C., higher nitric acid concentrations would be preferred, provided that acceptable structural materials are available. The higher nitric acid concentrations would increase the rates of graphite oxidation U) mole ratio necessary and would decrease the H N 0 3 / ( T h for complete dissolution of the thorium and uranium. The U) mole ratio required for their complete high H N 0 3 / ( T h dissolution in dilute nitric acid was probably due to the hydrolysis of their nitrate salts a t high temperature. Much more work \vi11 be required to determine whether the PAC process is applicable to fuels containing carbon-coated oxide particles. The limited experiments conducted to date showed that highdensity T h o 2 and T h O r U 0 2 microspheres are not readily dissolved in pressured nitric acid even when the H N 0 3 / T h mole ratio is 50 or greater. The fact that uranium and thorium oxides (and carbides) cannot be dissolved easily in dilute nitric acid a t high tempera-
(1) Farrell, J. B., Haas, P. A., “Pressurized Aqueous Combustion of Moderator Grade Graphite,” Division of Industrial and Engineering Chemistry, 150th Meeting, ACS, Atlantic City, N. J., September 1965. ( 2 ) Ferris, L. M., Bradley, M. J., “Off-Gases from the Reactions of Uranium Carbides with Nitric Acid at 90’ C.,” Oak Ridge Natl. Lab., ORNL-3719 (1964). 1 3 ) Howard. H. C.. in “Chemistrv of Coal Utilization.” H. H. Lowry, ed:, p. 346; LViley. New Ybrk, 1945. (4) Lane? J. A., MacPherson, H. G., Maslan, F., eds., “Fluid Fuel Reactors,” p. 99, Addison-St‘esley,Reading, Mass., 1958. (51 Nicholson, E. L., Ferris. L. M.. Roberts, J. T., “Burn-Leach Process for Graphite-Base Reactor Fuels Containing CarbonCoated Carbide or Oxide Particles,” Oak Ridge Natl. Lab., ORNL-TM-1096 (April 2, 1965). ( 6 ) Oak Ridge National Laboratory, “Homogeneous Reactor Program Quarterly Progress Report for Period Ending July 31, 1960,” ORNL-3004 (Oct. 28, 1960). ( 7 ) Savich, S. R., Howard, H. C., Znd. Eng. Chem. 44, 1409 (1952). ( 8 ) Teletzke, G. H., “Wet Air Oxidation,” 56th Annual Meeting, A.I.Ch.E., Houston, Tex., Dec. 1-5, 1963. ( 9 ) \Vhatley, M. E., et al., “Unit Operations Section Monthly Progress Report, March 1964,” Oak Ridge Natl. Lab., ORNLTM-887 (September 1964). (10) Zimmerman, F. J., Chem. Eng. 65, 117 (1958).
+
--f
+
+
\
,
RECEIVED for review August 18, 1965 ACCEPTEDFebruary 15, 1966 Division of Nuclear Chemistry and Technology, 150th Meeting, ACS, Atlantic City, N. J., September 1965. Research sponsored by the U. S.Atomic Energy Commission under contract with the Union Carbide Corp.
ELECTROCHEMICAL OXIDATION OF CHOLESTERYL ACETATE DIBROMIDE ABRAHAM COOPER’ AND CHARLES L. MANTELL Department of Chemical Engineering, Kewark College of Engineering, Newark, N . J .
c
has been prominent as a starting material for many functional derivatives. A number of researchers in steroid chemistry sought to convert this inexpensive product by oxidation of the groups attached to the nucleus, as well as 76,77,ZO-24). by degradation cf the side chain (3,4,6,8-77, Various reagents and systems have been used to oxidize cholesterol and its derivatives. A system of interest, use of a n HOLESTEROL
Present address, UOP Chemical Co., East Rutherford, N. J. 238
l & E C PROCESS D E S I G N A N D D E V E L O P M E N T
electrochemical cell, was reported by Kramli (75). The conditions specified by Kramli were duplicated and varied in an attempt to improve the results, with no success (5). The present paper reports achievements after modification of technique (5). Experimental
Raw Material Preparation. One hundred grams of cholesterol were refluxed with 200 ml. of acetic anhydride for
Cholesteryl acetate dibromide was dissolved in carbon tetrachloride, suspended with mixing in a 4.5M solution of sulfuric acid, and electrolyzed at a lead dioxide anode. The anodically prepared film of lead dioxide, when maintained at potentials (relative to a calomel electrode) above 1.5 volts, was a catalyst for the Oxidation. A new and mild oxidation at the catalytic electrode surface resulted in attack on the tertiary hydrogen atom at the 2 5 carbon. The mildness of the oxidation prevented decomposition of the unconverted raw material and permitted the recovery of up to 96% of the cholesteryl acetate dibromide and derivative!;. Conversion of starting material ranged from 30 to 55%. The products recovered after debromination were 25-hydroxycholesteryl acetate and 24-dehydrocholesteryl acetate mixed with 25-dehydrocholesteryl acetate. The molar yield of products ranged from 85 to 93%.
BROMINE -. .. .. CHOLESTERYL PCETATE 016ROMlOE
CHOLESTERYL ACETATE
CHOLESTEROL
I
I
ACETIC ANHYDRIDE STOCK SOLUTION
STOCK SOLUTION
,107. CAOBr t C C 1 4
E
2
EL E ClROLYS I S
t W(7.5) DEHYOROCHOLESTERYL ACETATE
1 hour. O n cooling, thle crystalline acetate separated. T h e mass was filtered and washed with glacial acetic acid. T h e wet crystals were dissolved in 1000 ml. of diethyl ether. T o this was added a solution of 16 ml. of bromine in 500 ml. of glacial acetic acid. After a few minutes of stirring, crystals precipitated. T h e mass was permitted to stand overnight. T h e crystal slurry was filtered and washed once with cold glacial acetic acid and then three times with petroleum ether (39' to 49" C . boiling range). T h e crystals were air-dried a t room temperature. Weight of the dry material was 130 grams. Melting point was 115' to 117' C. Fieser (9) reports 115.4' and 117.63 C. for two crystal forms. This material was stable to light and heat for periods up to 6 months in carbon tetrachloride solution. If stored as a dry powder it decomposed in less than a month. I n ethylene dichloride a r chloroform, the brominated ester decomposed in a few days to form dark red solutions. Electrolysis. The electrolysis was conducted by loading 250 ml. of 4.5M sulfuric acid in a 400-ml. porous Alundum beaker, placing a lead anode of 80 sq. cm. in the electrolyte, and surrounding this with a cathode chamber containing 200 ml. of 4.5M sulfuric acild with a lead wire cathode, and then pre-electrolyzing the anode a t low current density (1.5 ma. per sq. cm.) to form the lead dioxide film. After this film had been formed, the depolarizer, a solution of 2.5 grams of cholesteryl acetate dibromide in 25 ml. of carbon tetrachloride, was poured into the anode compartment. T h e anode compartment contained a glass cooling coil and a 0' to 100' C. thermometer. A calomel electrode was positioned in contact with the anode surface. Current densities were 62.5 to 250 ma. per sq. cm. Temperature varied from 30' to 40' C. Time of electrolysis was varied from 30 to 240 minutes (Table I). Debromination. At the end of a run the anode compartment was removed from the cell and the mixture was poured into a separatory funnel. T h e anode compartment was rinsed with 10 ml. of fresh carbon tetrachloride, which was combined
with the material in the separatory funnel. A lower layer was separated and transferred to an evaporating flask. The sulfuric acid layer was washed twice with 10-ml. portions of carbon tetrachloride and all the organic layers were combined. T h e acid layer was discarded. I t was found best to debrominate the reaction products as quickly as possible to avoid decomposition. Carbon tetrachloride was removed by evaporation a t room temperature a t reduced pressure (100 torr). Residue was dried and then dissolved in a mixture of 20 ml. of ethyl ether and 10 ml. of glacial acetic acid. Two grams of zinc dust were added a t room temperature while the solution was stirred. Mixing was continued for 15 minutes. At the end of this time, 3 drops of water were added to complete the reaction. T h e solution was decanted from the solids into a 100-ml. separatory funnel. Solids were washed twice with 5 ml. of ethyl ether and this was combined with the decanted liquid. T h e ether solution was washed four times with 50 ml. of water to remove all the acetic acid. T h e remaining ether solution was evaporated to dryness under vacuum (100 torr). Purification. T h e products of reaction were separated and purified by preparative thin-layer chromatography (74). Chromatoplates were prepared, five a t a time, from 400 X 200 X 3 mm. borosilicate glass. A mixture was prepared from 80 grams of Merck (Darmstadt) silica gel G and 160 ml. of tap water. This slurry was mixed for 60 seconds and then applied with a homemade plastic reservoir to the glass. Plates were vibrated to make the coating uniform. T h e plates were air-dried for 30 minutes on a flat surface and then transferred to a carrier. Plates and carrier were activated for 2 hours in a n electric oven a t 90" C., removed from the oven, and quickly placed in an airtight drying cabinet. T h e developing technique was worked out by pilot tests on 0.25-mm. thick silica gel G chromatographic plates. T h e most useful solvent-developing system was a 50 : 50 mixture of petroleum ether and benzene. Iodine vapor located the separated steroids on the test plates. T h e dry mixed acetates from the ether residue were dissolved in petroleum ether so that the concentration \.vas 10% (w./v.). A 2-ml. portion of this solution was applied across the 200-mm. width of a n activated chromatoplate. This plate was developed a t room temperature in a borosilicate glass tank saturated in the vapor space by pouring 400 ml. of the petroleum ether-benzene solution over a filter paper liner. Development time was 180 minutes. T h e developer solution was allowed to run the full 400-mm. length of the plate to achieve maximum separation of the components of the acetate mixture. T h e plate was removed and placed in a chamber that could be evacuated. T h e plate was placed in a hood and covered with a piece of glass over its entire surface, except for 5 mm. along one edge. This edge was developed with a pressurized spray of aqueous sulfuric acid containing formalin. T h e bands of silica that contained the three products were made visible by a color reaction; they were different shades of blue. T h e plate was removed from the hood and parallel scratches were made across the plate face where they had been located by the formalin solution. Each zone was then removed from the plate with a razor blade and collected separately in extraction flasks. Each of the three products collected was eluted from the silica with carbon tetrachloride. The material that had been collected from the front zone of the plate, and later proved to be cholesteryl acetate, was recrystallized from a minimum quantity of acetone. The second band of material, VOL. 5
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239
Table 1.
Electrolysis Data
Constant Conditions Pb/FbOZ, 80 sq. cm. 250 ml. of 4.5M H2S04 with 25 ml. of carbon tetrachloride containing 2.5 g. cholesteryl acetate dibromide Diaphragm Alundum beaker, 400-ml. Cathode Lead wire, '/*-inch diameter Catholyte 200 ml. 4.5M H2S04 Magnetic mixer 4 X 0.5 cm. diameter bar (approximately 50 r.p.m.) Anode Anolyte
EA = anode potential, volts (us. S.C.E.) e = time from start, minutes
.
Run 2. 40" C., 5 amperes, 63 ma. per sq. cm. 120 0 10 30 50 60 100 EA $ 5 . 0 + 4 . 0 0 + 3 . 3 0 $ 2 . 8 0 +2.50 $2 00 f l . 7 5 Cholesteryl acetate recovered. 0.88 g. Total dehydrocholesteryl acetate recovered. 0 . 8 7 g. Conversion. 51 . 570 Yield. 93%
e
Run 3. 30 ' C., 10 amperes, 126 ma. per sq. cm. 120 0 10 30 50 60 100 EA + 4 . 2 5 $3.70 +2 70 $2.15 $1.85 $ 1 . 2 0 i l . 15 Cholesteryl acetate recovered. 0 . 9 4 g. Total dehydrocholesteryl acetate recovered. 0 . 7 8 g. Conversion. 48. 7yG Yield. 89.0%
e
Run 4. 40 C., 10 amperes, 126 ma. per sq. cm. 120 0 10 30 50 60 100 E A $ 4 . 3 5 $3.70 + 2 . 8 0 + 2 . 2 0 + 1 . 9 0 $1.30 + 1 . 1 0 Cholestervl acetate recovered. 0 . 9 1 P. Total dehydrocholesteryl acetate recoGered. 0 . 8 2 g. Conversion. 50.07, Yield. 90.070 O
e
Run 5.
30" C., 15 amperes, 189 ma. per sq. cm. 120 10 30 50 60 100 EA $4.00 + 3 . 2 0 $ 2 . 3 0 f 1 . 6 5 + 1 . 5 0 + l . O O t0.80 Cholesteryl acetate recovered. 1.09 g. Total dehydrocholesteryl acetate recovered. 0 . 6 3 g. Conversion. 40.070 Yield. 86.570 0
Run 6. 40 C., 15 amperes, 189 ma. per sq. cm. 120 0 10 30 50 60 100 EA + 4 . 0 0 $ 3 . 3 0 $ 2 . 5 0 $1.75 $ 1 . 5 0 $ 1 . 1 0 $0.90 Cholesteryl acetate recovered. 1 .05 g. Total dehvdrocholestervl acetate recovered. 0 . 6 5 P. Conversiok 42.070 ' Yield. 85,070
e
-
30" C., 20 amperes, 252 ma. per sq. cm. 120 60 100 10 30 50 EA $ 3 . 5 0 $ 2 . 6 0 + 1 . 7 0 $1.00 + 0 . 7 5 + 0 . 4 5 $0.40 Cholesteryl acetate recovered. 1 .27 g. Total dehvdrocholestervl acetate recovered. 0 . 4 7 e. Conversioh. 30.070 ' Yield. 85.0%
Run 7.
e
0
-
e EA
Run 8. 40" C., 20 amperes, 252 ma. per sq. cm. 120 0 10 30 50 60 100 + 3 . 6 0 + 2 . 6 0 + 1 . 8 5 $ 0 . 9 5 +0.80 +0.45 $0.45
Cholesteryl acetate recovered. 1 .06 g. Total dehydrocholesteryl acetate recovered. 0.48 g. Conversion. 3 6 . 0 % Yield. 87.070 ~~
240
Equipment
T h e equipment has been described in detail ( 5 ) . Analytical Techniques
Run 1. 30" C., 5 amperes, 63 ma. per sq. cm. 100 120 30 50 60 e 0 10 EA + 4 . 8 0 + 4 . 0 0 $3.25 $2.70 $ 2 . 4 0 $ 1 . 8 0 $1.75 Cholesteryl acetate recovered. 0 . 8 2 g. Total dehydrocholesteryl acetate recovered. 0 . 9 0 g. Conversion 5 5 . 0 % Yield 90.470
e
which proved to contain a mixture of 24- and 25-dehydrocholesteryl acetate, was charcoal-treated first in benzene and then recrystallized from methanol. T h e material collected from the line of application on the chromatoplate was found to be 25-hydroxycholesteryl acetate, and was recrystallized from acetone after the carbon tetrachloride extract of the silica gel had been carbon-treated and evaporated to dryness.
I & E C PROCESS D E S I G N A N D D E V E L O P M E N T
The analytical techniques have been described ( 5 ) . Molecular weights were determined on a mass spectrometer, CEC Model 21-103. Carbon and hydrogen analyses were run in a Model 185 F & M analyzer. However, there were inaccuracies due to improper drying of the chromatographic column. Consequently these analyses were repeated by a standard microcombustion technique. Discussion
After all conditions for electrolysis had been standardized by elimination of unworkable anodes, solvents, and systems, experiments were conducted with PbOz anodes with the raw material in a saturated carbon tetrachloride solution suspended in 4.5M sulfuric acid. Attempts were made to conduct experiments a t constant anode potential. However, when the potential was stabilized, the cell current rapidly fell to zero, with no appreciable production of useful material. T o produce substantial oxidation, all subsequent runs were a t constant current density. T h e data in Table I are similar to the results of Ruetschi and Angstadt (78), who reported the preparation of a lead oxide anode in 4 . 3 M sulfuric acid a t 30' C. Lead dioxide, formed electrolytically, exists in orthorhombic a and tetragonal p crystal forms. Conditions for the formation of these two types have recently been the subject of a number of studies (2, 20). Kiseleva and Kabanov (73) suggested that the p form is a consequence of H z S 0 4 chemisorption on the lead dioxide formed during anodic oxidation of lead. This explanation is challenged by Baker (7). An analysis by Ruetschi and Angstadt (78) indicates that initially a P b S 0 4 film is formed. As this film grows to a critical thickness, it is accompanied by a critical ohmic drop, so that sod-' and H + ions are unable to penetrate the film easily. Any decrease in SO4-*ions causes a corresponding equivalent loss of H + ions because the system must remain electrically neutral. In the dense PbS04 layer, a high electric field is established with consequent large voltage drop, and tends to repel H + ions from the microcavities of the inner part of the film and to attract S 0 4 - 2 ions and OH- ions formed by dissociating water molecules. This causes the p H to stabilize a t a high value in the interior of the corrosion film. The p H gradient across the film is assumed to be abrupt after ionic diffusion has stopped and the reaction a t the electrode limited by mass transport. The p H rises quickly to the point where OH- ions will be available to oxidize lead to PbO or hydrated forms such as 5 P b 0 . 2 H z O . These divalent lead compounds are rapidly oxidized to a-PbOz. This oxidation of PbO to a-PbOs in the corrosion film takes place above -0.3 volt (us. STP H z ) , As the electrode potential is raised, the outer sulfate layer and the PbO film increase in thickness as the ohmic drop increases. At high enough potentials, lead sulfate may be oxidized to PbOz in the more acidic outer part of the corrosion layer. At a p H of 2 in the
interior of the film, P b S 0 4 could be oxidized to PbOz a t a potential of +0.7 volt (referred to standard calomel electrode). At the higher anodizing potential, P-Pb02 is present in the outer filni. T h e current efficient-y would indicate whether the reaction is truly electrochemial. For example, in one experiment made a t 62.5 ma. per sq. cm. for 1 hour, the total energy used was 5 ampere-hours. For a 1-electron reaction, there should be produced 5/26.8 ‘x 444.7 = 83 grams of 25-hydroxycholesteryl acetate which would have dehydrated to form 80 grams of 24-dehydrocholesteryl acetate. Since only about 1 gram was formed a t most, the process has a 1.2% efficiency. I t was necessary to check the stability of the raw material under the conditions of the oxidation. When duplicate samples were run in 4.5iM sulfuric acid with no current, the cholesteryl acetate dibromide was not hydrolyzed or degraded. Thin-layer chromatograms showed only cholesteryl acetate present after debromination of the reaction mass. Debromination did not cause oxidation. No oxidation occurred in carbon tetrachloride solution that contained varying amounts of chemically produced lead dioxide. In suspension in 4.5M sulfuric acid, which contained lead dioxide, conversions in the range of 570 were obtained. When the lead anode was oxidized in sulfuric acid with the electric current and the current was then shut off, injection of the raw material into the cell did not yield any product. Since all the useful conversion was performed a t anode potentials substantiallv above 2.5 volts, it appears that the catalytic agent invo1vc:d in the oxidation was the /3 form of lead dioxide. Conversion is directly correlated with anode potential. T h e best conversions occurred when cell conditions permitted the highest anode potential. Lead dioxide produced by chemical reaction a t low temperature could, according to Burbank ( Z ) , consist mainly of the a configuration, but could be converted to the /3 form in air a t approximately 300“ C. This would account for the relatively small conversion with reagent grade lead dioxide. Subsequent chemical treatment of the reaction mass was not responsible for oxidation of the raw material, as shown by a n infrared spectrum. T h e spectrum of the starting material was superimposed on the spectrum of the reaction mass. The carbon-bromine absorption occurs above 15 microns and does not interfere with the results. T h e peaks a t 7.8 and 11.4 microns are identified as the 24dehydro-vicinal double bond system. A peak occurs a t 7.8 microns in the reactior mass. Properties of Products. T h e products of reaction were identified by melting points, optical rotations, molecular weights, infrared spectra, and carbon and hydrogen content (Table 11). Ryer (7!?) assumed that 25-hydroxycholesteryl acetate was completely dehydrated to the 25-dehydro derivative. Dauben and Bradlow (7) made the same assumption, although they used phosphorus tribromide in benzene in the dehydration. Idler and Fagerlund (72) proved that the other workers had produced mixtures of 24- and 25-dehydrocholesteryl acetate. Fair agreement is shown with the d a t a of Ryer (Schering), since the milligram quantities of material used for identification were supplied by Schering. Chromatographs obtained with the Perkin-Elmer 811 apparatus show the two peaks of the 24- and 25-dienes. Chromatograms and related data detail are available in microfilm (5).
Table II. Properties of Reaction Products Cooper Ryer ( 79) Dauben ( 7 ) Idler ( 7 2 ) ~
M.P., ff20
O
C.
6
24(~~)-DEHYDROCHOLESTERYL ACETATE 91-94.0 93.5-94.0 92.5112 93.5 -43.4’ -43.6’ -42.8 ’ -44.4’
Analysis. Calculated for C29H4e02: C, 81.63; H, 10.87 Found C 80.80 81.39 81.64 81.60 H 10.70 11.08 10.63 10.72 M.W. Calculated 426.7 426 From mass spectrum Found M.P.,
C.
b
25-HYDROXYCHOLESTERYL ACETATE 140-41 140.2138.541.2 40.0 -40.8 -40.4 -42.1
Analysis. Calculated for Cz9Hds03: C, 78.32; H, 10.88 Found C 78.25 78.15 78.80 10.66 10.56 H 11.09 M.W.
Calculated 444.7 Found 444 From mass spectrum a 25-Dehydrocholesteryl acetate. 2% chloroform solution.
Conclusions
Factors involved are the conditions for electrolytic oxidation. The products of the reaction after debromination were 24- and 25-dehydrocholesteryl acetate, the intermediate 25-hydroxycholesteryl acetate, and unreacted cholesteryl acetate. T h e technique included oxidation of cholesteryl acetate dibromide in saturated (1097,) solution in carbon tetrachloride, suspended by mixing in a 4.5M sulfuric acid a t 30’ and 40’ C. over a range of current density from 62.5 to 250 ma. per sq. cm., a t an electrochemically prepared lead dioxide anode in a n Alundum diaphragm cell. The specific condition of anode potential maintained electrically above 2.5 volts (relative to a saturated calomel electrode) resulted in the lead oxide phase of B configuration (tetragonal). Over this range of conditions it was possible to recover products and starting material equivalent to 96% of the starting dibromide. Conversion of raw material ranged from 30 to 55%. T h e molar yield of products based on cholesteryl acetate dibromide ranged from 85 to 93%. literature Cited (1 ) Baker, R. A,, J. Electrochem. SOC.109, 338 (1962). ( 2 ) Burbank, Jeanne, Ibid., 106, 369 (1959).
(3) Butenandt, A,, Dannenbaum, H., Kudszus, H., Z. Physiol. Chem. 237, 57 (1935). (4) Cook, R. P., “Cholesterol,” Academic Press, New York, 1958. (5) Cooper, Abraham, D.Sc. thesis, Newark College of Engineering, Newark, N. J., 1965; University Microfilms, Inc., 313 N. First St., Ann Arbor, Mich. 48107. (6) Cornforth, J. W., Hunter, G. D., Popjak, G., Biochem. J . 54, 590 (1953). ( 7 ) Dauben, W. G., Bradlow, L. H., J. A m . Chem. SOC.72,4248-50 (1950). (8) Dauben, W. G., Payot, P. H., Ibid., 78,5657-60 (1956). (9) Fieser, L. F., Fieser, M., “Steroids,” p. 536, Reinhold, New York. 1959. (lO)-Fieser, L. F., Huang, W.-Y., Bhattacharyya, B. K., J. Org. Chem. 22, 1380-4 (1957). (11) Gollnick, K., Neumeuller, A. D., Ann. 603, 46 (1957). (12) Idler, D. R., Fagerlund, J. H. M., J. A m . Chem. Sot. 79, 1988-91 (1957). (13) Kiseleva. I. G.. Kabanov. B. N.. Akad. Nauk USSR Dokl. 108, 864 (1956). ’ I
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(14) Korzun, B. P., Dorfman, L., Brody, S. M., Anal. Chem. 35, 950-2 (1963). (15) Kramli, Andras, Arch. Biol. Hung. 1711, 337 (1947). (16) Maas, S. P. J., deHeuss, J. G., Rec. Trau. Chim. 77, 531 (1958). (17) Mauthner, J., Suida, W., Monatsh. 17, 579 (1896). (18) Ruetschi, P., Angstadt, R. T., J. Electrochem. Sod. 111, 1329 (,-I 964). (19) Ryer, A. I., Gebert, W. H., Murill, N. M., J. Am. Chem. SOC. 72, 4247-8 (1950).
(20) Wallis, E. S., Fernholz, E., Ibid., 57, 1379, 1504 (1935). (21) Westphalen, T., Ber. 48, 1064 (1915). (22) Wieland, P., Miescher, K., Helv. Chim. Acta 31,211 (1948). (23) Windaus, A., Be?. 40,257 ( 1 907). (24) Wintersteiner, O., Bergstrom, S., J. Biol. Chem. 137, 785 (1941).
. I .
RECEIVED for review August 16, 1965 ACCEPTED March 11, 1966
EXPERIMENTAL STUDY OF THE EFFECTS OF TEMPERATURE AND ULTRA-HIGH PRESSURE ON THE COALIFICATION OF BITUMINOUS COAL LIN-SEN PAN, TERRELL N. ANDERSEN, AND HENRY E Y R I N G Rate Processes Institute, University of Utah, Salt Lake City, Utah
Artificial coalification of high volatile bituminous coal was experimentally effected by heating the coal (at temperatures up to 850’ C.) at pressures of 30 kilobars. Such samples were compared with coal heated at atmospheric pressure and also with standard coal samples of various ranks, by means of ultimate analysis, x-ray spectroscopy, IR spectroscopy, and electrical resistivity. The above tests indicate that heat breaks off fragments (“volatiles”) of the coal structure, and drives them off as gases, while high pressure causes retention of many of these products through retardation of bond breakage or through reactions which condense them onto the coal structure. The structure of coal, subjected to elevated temperatures and pressures, tends toward that of higher rank coals, while the product of low pressure heating tends toward coke.
HE ORDINARY PROCESS of coalification of a n accumulation of T o r g a n i c debris is generally considered to embrace two stages of prime importance (6, 75, 79, 25): (a) the putrefaction (biochemical) stage, which probably leads no further than the formation of peats, humus, humic concentrates, etc., and ( b ) the alteration or metamorphic (dynamochemical) stage. T h e latter stage converts the coalifying material into lignite, bituminous (humic) coals, and anthracite coals. Such transformations as ( 6 ) are the direct or indirect result of geodynamic influences ranging from pressure-dehydration to graphitization. T h e influence of pressure in the last stage ( b ) is not well understood as most evidence for the mechanism of coalification is based upon field observations and distillation studies. Davis and Spackman (8) have made coal-like material from the wood of Taxodium distichurn (bald cypress) in a basic medium with a uniaxial pressure device, at pressure up to 5 kilobars (kb.) and temperatures up to 400’ C., and have shown that those changes in the so-called “biochemical stage” of coal formation could actually have been largely nonbiochemical. Straw has been heated a t temperatures of about 300’ C. and pressures of several hundred atmospheres in the presence of limestone to produce a substance which has coal-like properties (26). T h e purpose of the present study was to investigate the role of pressure in the metamorphic stage ( b ) of coalification. High volatile (hv) bituminous coal was subjected to pressures u p to 30 kb, and temperatures u p to 850’ C., and was then compared with the initial material and with natural coals of various ranks by means of x-ray diffraction, ultimate analysis, infrared spectroscopy, and electrical resistivity. T h e sources of the coal samples studied and those used as references are listed in Table I. Anthracite “A” was used for
242
I&EC PROCESS D E S I G N A N D DEVELOPMENT
all tests except the x-ray diffraction, in which case A’ was used. This was because sample A’ gave a n x-ray pattern much more like those of anthracite’s in thc literature. Sample A, on the other hand, produced other measurements typical of anthracites. T h e purposes of the extreme pressures and temperatures used were to effect rapid and drastic changes which could easily be studied experimentally in reasonable lengths of time and to provide greater pressures than existent “geostatic” pressures a t coal beds, since the latter may not be those effective in actual coalification (owing to horizontal earth movements) (7, 25). Experimental Procedure
T h e coal as received was ground (wet) with a 4-inch diameter ball mill to -100 mesh, dried in the atmosphere, and then heated a t 105’ C. for 1 hour. Those samples used as references were ground to -250 mesh in the above manner. High volatile bituminous coal samples were then subjected to various pressures and temperatures in a n unsupported pistoncylinder press. T h e essential features of the sample pressure chamber used are shown in Figure 1. Details have been recorded elsewhere of this ( 7 7) and similar arrangements (2, 77) of the pressure and recording apparatus. Inside the 1-inch Table I. Sources of Coal Samples and Standards Sample Sources of Coal Buck Mt. Seam, Pa. A. Anthracite Russia A‘. Anthracite Mercer County, Southern W. B. Pocahontas
.
V2
C. D.
Low volatile bituminous High volatile bituminous
I .
Pocahontas Seam No. 4, W. Va. Spring Canyon, Utah
